1. Field of the Invention
The present invention relates to a printed-wiring board and more particularly to a printed-wiring board provided with solder-resist barriers, the top surface level thereof being higher than the surface level of lands, disposed on a solder-resist layer formed on the conductor pattern.
2. Description of the Prior Art
A selective soldering type printed-wiring board is fabricated by arranging a conductor pattern of copper foil circuits on an insulating board and forming a solder-resist layer on the copper foil circuits excluding the lands belonging to the conductor pattern. Such a solder-resist layer is shown in a schematic sectional view of FIG. 2, wherein liquid resin is spread over a conductor pattern 2 arranged on an insulating board 1 excluding lands 21, 21 . . . and forms a solder-resist layer 3. Since the printed-wiring board provided with the solder-resist layer 3 thereon has the lands 21, 21 . . . of a required minimum area, there are such advantages that the board does not become stained with solder, the adhesive strength of the copper foil circuit is not lowered by heat, and the consumption of solder can be saved. On the other hand, since the solder-resist layer 3 is frequently formed at a level lower than that of the upper side of the lands 21, 21 . . . , there is a disadvantage that a solder bridge (short circuit) is liable to be produced between circuits. Therefore, it is practiced to dispose protruding members 4, 4 . . . on the top surface of the solder-resist layer 3 by such a method as silk screen printing. However, since the setting speed of the silk ink is not fast enough, the protruding members 4, 4 . . . provided by such a method as silk screen printing tend to spread out with time, and so, the same are frequently built at a lower level than that of the lands 21, 21 . . . .
While the lands 21, 21 . . . made of copper foil has, for example, a thickness of approximately 35 .mu.m, the solder-resist layer 3 is 12-15 .mu.m thick. Since the height of the protruding members 4, 4 . . . formed of the liquid silk ink becomes 12-15 .mu.m, the sum of the height of the solder-resist layer 3 and that of the protruding member 4, i.e., the height of the top portion of the protruding member 4, is held below that of the land 21. Therefore, it has not been possible to effectively prevent the occurrence of the solder bridging between adjoining lands.